1. Field of Invention
The present invention relates to a structure. More particularly, the present invention relates to a package structure.
2. Description of Related Art
In power converter, included ballast and motor driver, half bridge switch is often involved. Half bridge switch is a series of two switches (low side and high side switches) connected between positive and negative pole of dc electrical bus. The two switches action complementary so the node in between the switches is either connected to positive pole or negative pole of dc electrical bus.
For those switches, Transistor, MOSFET or IGBT are often used. They are three-terminal devices. Connecting and breaking of the switch is between two of those terminals. The control for connecting or breaking (on/off signal) is applied between two terminals, so one of those terminals should be in common. The common terminal is emitter, source or emitter for transistor, MOSFET or IGBT, respectively. The controlling terminal is base, gate or gate for the respective device. The last terminal is collector, drain or collector, respectively.
In most applications, the common terminal of lower switch is coupled to negative pole, and so is the controller's ground, so its on/off signal may be direct applied to controlling terminal. However, for high side switch, whose common terminal is swinging between positive and negative pole of dc electrical bus, so its control signal need to be float, moving relative with its common terminal. The conventional method uses pulse transformer or photo-couple. For performance and cost, recently developed semiconductor high side driver is becoming popular.